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Here finally is the document I remembered reading a long time ago, but could not remember where I saw it.
This will prove to be helpful to many! Thanks to Roland at AstroPhysics.....
Peter
Determining what spacing change is needed:
Step 1: focus exactly on a star in the center of the frame. Note the exact focus position.
Step 2: focus on a star at the corner of the frame and note the exact focuser position.
If the focuser moves out (away from the scope) in Step 2, then the field flattener is overcompensating and the focal plane of the camera must move inward - shorten the distance from flattener to the camera.
If opposite occurs, then lengthen the distance.
This can be done in steps of 1 - 2 mm at a time until the field is flat. This is the only way to get precise flat field.
The Quad TCC was made for 35 mm format, but it can be used with larger 16803 KAF sensors if the spacing is reduced slightly. The amount of reduction is typically 1 - 3 mm
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